Automatic drain valve for a floating roof

ABSTRACT

Automatic drain valve for mounting in a self-buoyant roof that is used with an atmospheric storage tank containing a liquid. The valve includes an orifice and a larger disk, located under the orifice. There is a float attached to the disk so that the valve is biased closed unless some liquid gathers on top of the roof. Under the latter circumstances the valve will open and allow the liquid to drain through the roof into the tank beneath.

United States Patent 1 Fisher [451 May 13,1975

1 1 AUTOMATIC DRAIN VALVE FOR A FLOATING ROOF [75] Inventor: Walter Fisher, Willowdale, Ontario,

Canada [73] Assignee: Texaco Canada Limited, Montreal,

Canada [22] Filed: Apr. 22, 1974 [21] Appl. No.: 462,913

[52] US. Cl 220/219; 220/227 [51] Int. Cl B65d 87/18 [58] Field of Search 220/26 R, 26 D, 219, 227;

[56] References Cited UNITED STATES PATENTS 1,116,931 Schutt 137/202 2,560,586 7/1951 Michaels 220/26 R 3,329,301 7/1967 Lee 3,815,775 6/1974 Strunc 220/26 R Primary ExaminerAlan Cohan Attorney, Agent, or Firm-T. H. Whaley; C. G. Ries; Henry C. Dearborn [57] ABSTRACT Automatic drain valve for mounting in a self-buoyant roof that is used with an atmospheric storage tank containing a liquid. The valve includes an orifice and a larger disk, located under the orifice. There is a float attached to the disk so that the valve is biased closed unless some liquid gathers on top of the roof. Under the latter circumstances the valve will open and allow the liquid to drain through the roof into the tank beneath.

1 Claim, 2 Drawing Figures AUTOMATIC DRAIN VALVE FOR A FLOATING ROOF BACKGROUND OF THE INVENTION l. Field of the Invention This invention concerns floating roofs for atmospheric storage tanks, in general. More specifically, it relates to an automatic drain valve in combination with a floating-type roof.

2. Description of the Prior Art It has been found that where storage tanks employ a floating type of roof, and particularly under certain conditions, the liquid material in the tank may inadvertently be carried on to the deck, or top, of the floating roof. Under such circumstances the roof may sink and create costly difficulties in retrieval or in rectifying the situation. Consequently, it is an object of this invention to provide the combination with a floating roof of an automatic drain valve which will act to permit any liquid on top of the roof to flow through and join the liquid inside the tank. Under normal circumstances the valve is held closed to maintain the integrity of the roof.

SUMMARY OF THE INVENTION Briefly, this invention concerns an automatic drain valve adapted for mounting in a buoyant member, to permit flow of a buoyancy fluid from above said member down to beneath said member. Such a valve comprises an orifice for permitting said buoyancy fluid flow therethrough when open, and a closure member adapted to cooperate with said orifice for maintaining the valve closed under normal conditions. It also comprises means for mounting said closure to cause opening thereof whenever a predetermined amount of said buoyancy fluid is located on top of said buoyant member at said valve location.

Again, briefly, the invention relates to structure that is in combination with a buoyancy-type floating roof for an atmospheric liquid storage tank. The structure concerns an automatic drain which comprises a circular housing mounted integrally with said roof, the said housing incorporating a flat partition located midway relative to the thickness of said roof. It also comprises a closure member for maintaining said orifice closed under normal floating conditions of said roof. The said closure member comprises a flat disk having a diameter greater than the diameter of said orifice and being located underneath said partition. It also comprises a vertically situated shaft under normal floating conditions of said roof, and having said flat disk attached centrally thereon, and a pair of diametrically located strips having bearings centrally attached thereto for slidably supporting said shaft and disk for free vertical movement. It also comprises a float attached to the bottom of said shaft situated below the lower end of said strips, and having sufficient buoyancy when immersed in said liquid to bias said disk into closing contact with said partition.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing and other objects and benefits of the invention will be more set forth below in connection with the best mode contemplated by the inventor of carrying out the invention, and in connection with which there are illustrations provided in the drawings, wherein:

FIG. 1 is a cross-sectional view partly in elevation showing a valve according to this invention; and

FIG. 2 is a top plan view of the valve illustrated in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the use of buoyancy-type floating roofs for atmospheric storage tanks, it has been found that some of the stored product may be carried on to the deck of such a floating roof. Such conditions cause substantial and costly difficulties, sometimes even causing a sinking of the roof. By making use of a valve which is adapted for use with such roofs, the harmful conditions may be readily avoided while still maintaining the closure effect of the roof.

Thus, referring to FIG. 1, there is illustrated a fragmentary portion of a buoyancy-type roof 11 which has mounted therein an automatic drain valve 14 according to this invention. It will be observed that the roof 11 is supported by, and is floating on, a body of liquid product 12. Under normal conditions the roof 11 will have sufficient weight to cause the product level to be somewhat above the bottom of the roof 11, as is indicated by an arrow 13 in FIG. 1.

The valve structure includes a circular housing 16 which may be fitted closely into the body of the roof 1 1 by having upper and lower flanges 17 and 18 which are countersunk so as to be flush with the top and bottom surfaces, respectively, of the roof ll. Centrally located in a vertical sense, relative to the thickness of the roof 11, there is an integrally formed partition 21 that has an axially centered orifice 22 formed therein. Orifice 22 acts as the passageway for permitting flow-through of any liquid that may gather on top of the roof 11. Such liquid will, of course, flow into a hollow space 23 within the housing 16 and above the partition 21.

Coaxially located with the orifice 22 and housing 16, there is a flat disk 26 that is securely attached to a shaft 27 in any convenient manner, e.g., by means of a setscrew 28 in a collar 20. Collar 29 is integrally attached to the disk 26 in any feasible manner, e.g., by welding.

The shaft 27 is supported for free sliding movement by a pair of bearings 32 and 33 that are mounted on a pair of diametrically located strips 34 and 35, respectively.

Attached to the lower end of the shaft 27, there is a float 38 that is designed of a material and with the necessary volume to create a buoyancy sufficient to overcome the weight of all attached elements, including the shaft 27, disk 26 and an upper stop-collar 39 that may be attached to the shaft 27 near the upper end thereof. Such buoyancy force will, of course, be effective whenever the float 38 is immersed in the liquid product 12. Consequently, under normal conditions, the orifice 22 will remain closed by having the larger-diameter disk 26 biased upward against the partition 21 around the edges of the orifice.

OPERATION Whenever liquid gathers on top of the float 11, it will flow into the space 23 and, consequently, onto the portion of disk 26 that is exposed by the orifice 22. As soon as sufficient of this liquid gathers in the space 23 to overcome the buoyancy of the float 38, the disk 26 and the attached elements including the shaft 27 will be forced downward so as to open the orifice 22. Then, of

course, the liquid may flow through the orifice and over the edges of the disk 26 to join the body of liquid product 12 within the tank.

It may be observed that occasionally where the product in the tank that employs a buoyancy-type roof is quite volatile, there may be times when gas bubbles form underneath the roof which would tend to lift the roof and, consequently, might cause tipping or other undesired conditions. However, by proper design of a valve structure according to this invention, the gas bubbles should be released as soon as the roof 11 is lifted above the body of liquid 12 far enough to lift float 38 out of the liquid. In other words, even though the valve will tend to remain closed because of the upper pressure of a gas bubble, the buoyancy force of float 38 when immersed in liquid, will become a negative, or downward force as soon as it is lifted out of the liquid, and this will be enough to open the valve and allow the gas in the bubble to escape.

While the invention has been described above in considerable detail and in accordance with the applicable statutes, this is not to be taken as in any way limiting the invention, but merely as being descriptive thereof.

I claim:

1. In combination with a buoyancy-type floating roof for an atmospheric liquid storage tank, an automatic drain comprising a circular housing mounted integrally flush with the top and bottom surfaces of said roof,

said housing incorporating an integral flat partition located midway relative to the thickness of said roof and having a cylindrical walled circular orifice coaxially located therein, and

a closure member for maintaining said orifice closed under normal floating conditions of said roof,

said closure member comprising a thin flat disk having a cylindrical edge with the diameter thereof greater than the diameter of said orifice and being located underneath said partition,

a vertically situated shaft under normal floating conditions of said roof and having said flat disk attached centrally thereon,

a pair of diametrically located relatively narrow strips having bearings centrally attached thereto for slidably supporting said shaft and disk for free vertical movement, and

V a float attached to the bottom of said shaft situated below the lower one of said strips and having sufficient buoyancy when immersed in said liquid to bias said disk into closing contact with said partition. 

1. In combination with a buoyancy-type floating roof for an atmospheric liquid storage tank, an automatic drain comprising a circular housing mounted integrally flush with the top and bottom surfaces of said roof, said housing incorporating an integral flat partition located midway relative to the thickness of said roof and having a cylindrical walled circular orifice coaxially located therein, and a closure member for maintaining said orifice closed under normal floating conditions of said roof, said closure member comprising a thin flat disk having a cylindrical edge with the diameter thereof greater than the diameter of said orifice and being located underneath said partition, a vertically situated shaft under normal floating conditions of said roof and having said flat disk attached centrally thereon, a pair of diametrically located relatively narrow strips having bearings centrally attached thereto for slidably supporting said shaft and disk for free vertical movement, and a float attached to the bottom of said shaft situated below the lower one of said strips and having sufficient buoyancy when immersed in said liquid to bias said disk into closing contact with said partition. 